Friction clutch and drive system for cooling an internal combustion engine of a vehicle with a friction clutch

ABSTRACT

A friction clutch ( 5 ) having a drive side and an output side which can be used to drive a fan impeller ( 2 ), and a selectively engageable friction disk clutch ( 13 ), which in the engaged state connects the output side to the drive side, and a first eddy current clutch ( 15 ) for providing a slip speed on the output side, the first eddy current clutch ( 15 ) having an eddy current zone formed on a cooling ring ( 11 ), wherein an eddy current zone for a second eddy current clutch ( 18 ) is provided on the same cooling ring ( 11 ) on which an eddy current zone for the first eddy current clutch ( 15 ) is formed.

The invention relates to a friction clutch and to a drive system withsuch a friction clutch.

STATE OF THE ART

Friction clutches of the type described above are already known in avariety of different forms.

The unexamined German application 4 207 710 A1 discloses anelectromagnetically actuated friction clutch, which serves to drive afan impeller for a cooling fan. The fan impeller is here intended to bedriven at the direct speed of the drive unit and with two different slipspeeds. A first electromagnetic friction disk clutch is provided toproduce the direct speed and a second electromagnetic friction diskclutch is provided in conjunction with a first eddy current clutch toproduce a first slip speed. A further eddy current clutch serves toproduce a second slip speed.

OBJECT AND ADVANTAGES OF THE INVENTION

The object of the invention is to provide a friction clutch of compact,versatile construction.

This object is achieved by the features of the invention as discussedherein.

Advantageous and appropriate developments of the invention are alsospecified in the disclosure to follow.

The invention first proceeds from a friction clutch having a drive sideand an output side, which can be used to drive a fan impeller. Thefriction clutch comprises a selectively engageable friction disk clutch,which in the engaged state connects the output side to the drive side.In addition a first eddy current clutch is intended to provide a slipspeed on the output side, the first eddy current clutch having an eddycurrent zone formed on a cooling ring. The slip speed then ensues whenthe friction disk clutch is not engaged.

The core of the invention resides in the fact that an eddy current zonefor a second eddy current clutch is provided on the same cooling ring onwhich an eddy current zone for the first eddy current clutch is formed.

This allows heat generated by the eddy current clutches to beefficiently dissipated via one component. The cooling ring is analuminum ring, possibly comprising cooling fins, for example, in which asteel insert, for example, which brings about a desired field conductionof the eddy currents generated in the eddy current zones, is arrangedbehind the respective eddy current zone.

Opposite the respective eddy current zone there is preferably arotatable element provided with permanent magnets, for example a carrierring fitted with permanent magnets, which induces corresponding eddycurrents in the eddy current zones.

The friction clutch is preferably designed so that although on thecooling ring there are eddy current zones available for two eddy currentclutches, a full functionality is also afforded with only one eddycurrent clutch operative.

Where the second eddy current clutch is fully embodied with acorresponding permanent magnet carrier, this clutch can preferably beengaged by way of a friction clutch, for example, so that altogetherthree speeds are possible. In the case of a first slip speed thefriction clutch and the second selectively engageable eddy currentclutch are disengaged, so that a connection from the drive side to theoutput side exists only through the first eddy current clutch. A furtherslip speed, higher than the first slip speed, can be achieved byadditionally engaging the second eddy current clutch.

Finally, the drive side is frictionally connected to the output side byengaging the friction disk clutch. A third speed is thus obtained, whichwith full frictional grip is equal to the drive speed.

The friction disk clutch and/or the second eddy current clutch may bepneumatically or hydraulically operated.

In a particularly preferred development of the invention the frictiondisk clutch and/or the second eddy current clutch can beelectromagnetically engaged and disengaged. For this purpose an armaturedisk, which may be mounted so that it is axially moveable, for example,may be drawn towards a rotor by an electrically generated magneticfield, of a coil for example, so that a frictional connection is formedbetween the armature disk and the rotor.

The rotor preferably constitutes an output side of the friction clutch.

In this case the cooling ring preferably forms the drive side of theclutch. Besides the scope for a very compact construction, this has theadvantage that cooling of the eddy current clutches is optimized, sincethe drive side always rotates at drive speed.

By contrast the speed of the output side varies according to the engagedstate of the clutch.

The eddy current areas on the cooling ring are preferably arrangedoverlapping in a radial direction, for example overlapping so that theyare radially congruent. A compact construction can thereby be furtherimproved.

Both the second eddy current clutch and the friction disk clutch have aseparately moveable armature disk.

It is moreover feasible to provide two separate magnetic fieldconduction means in the cooling ring. For example a magneticallyconductive steel ring is cast into the cooling ring behind radiallyoutwardly overlapping eddy current zones. This contributes to anoptimization of the magnetic field, which is induced by the eddycurrents.

A friction clutch as described can be used in a drive system for thecooling of an internal combustion engine in a vehicle, for example amotor vehicle, in which a fan impeller and a drive side of the fanimpeller are connected by the clutch.

An angular gear mechanism may moreover be provided between the fanimpeller, which acts on a radiator of an internal combustion engine, forexample, and the clutch. Account can thereby be taken of the spatialarrangements of assemblies in the engine compartment of a motor vehicle,for example.

In the case of a drive system for the cooling of an internal combustionengine of a vehicle, in which a gear mechanism, in particular an angulargear mechanism, and a clutch, for example a clutch as described above,are provided, it is furthermore essential for the invention that theclutch directly abuts the angular gear mechanism on the drive side andis in particular directly affixed thereto (for example, flange-mountedthereon). The connection is preferably such that there are no exposedshaft sections. A robust, compact unit can thereby be achieved, which inhard operational service possesses stability and great resistance to anypossible external influences.

DRAWINGS

Several exemplary embodiments of the invention are represented indrawings and are explained in more detail below, indicating furtheradvantages and details.

In the drawings

FIGS. 1-4 each in highly schematic side views show a friction clutchaccording to the invention with an angular gear mechanism for driving afan impeller in front of a radiator unit.

DESCRIPTION OF THE EXEMPLARY EMBODIMENTS

FIG. 1 represents a drive system 1 for a fan impeller 2, which ispositioned, for example, in front of a radiator 3 of an internalcombustion engine (not shown) of a motor vehicle, for example a bus. Thedrive system 1 comprises an angular gear mechanism 4 and anelectromagnetically actuated friction clutch 5. The friction clutch 5 islocated directly against the angular gear mechanism 4, for examplemounted directly on the angular gear mechanism 4. The angular gearmechanism 4 comprises an output shaft 6, which is connected to the fanimpeller 2.

On the drive side the friction clutch 5 comprises a drive shaft 7 and onthe output side an output shaft 8, which is led into the angular gearmechanism 4.

Two gearwheels 9, 10 set at an angle to one another are provided in theangular gear mechanism.

The friction clutch comprises a cooling ring 11, which is rotationallyfixed to the drive shaft 7. Also rotationally fixed to the cooling ring11 is an axially moveable armature disk 12 of a friction disk clutch 13.Situated opposite the armature disk 12 is a rotor 14 of the frictiondisk clutch, which is rotationally fixed to the output shaft 8. Thearmature disk 12 can be attracted to the rotor 14 by an electromagnet(not shown), thereby allowing a direct connection of the drive shaft 7to the output shaft 8.

In addition a first eddy current clutch 15 is arranged between the driveshaft 7 and the output shaft 8, a carrier 17 fitted with permanentmagnets 16 being rotationally fixed to the output shaft 8. The permanentmagnets interact with an opposing eddy current zone on the cooling ring11, so that a drive torque can be generated.

A speed differential between the drive shaft 7 and the output shaft 8 isnecessary for this purpose.

Finally a second eddy current clutch 18, which in contrast to the firsteddy current clutch 15 is selectively engageable, however, is providedin the friction clutch 5.

For this purpose the second eddy current clutch 18 has an armature disk19, which is axially moveable and which under corresponding magneticforces can be attracted to the rotor 14.

If the friction disk clutch 13 and the second eddy current clutch aredisengaged, the drive shaft 7 drives the output shaft 8 at a slip speedby way of the first eddy current clutch 15.

If the second eddy current clutch 18 is additionally activated byattraction of the armature disk 19, the permanent magnets 21 fitted on acarrier 20 can interact with a second eddy current zone formed on thecooling ring 11 in the event of a speed differential between the driveshaft 7 and the output shaft 8, which means that the output shaft 8 isdriven at a speed somewhat greater than the slip speed. The second eddycurrent clutch 18 takes on an additional drive torque, so to speak,which affords a second slip speed.

It is important here that both eddy current zones are provided on thecooling ring 11, which always turns at the speed of the drive shaft 7.

This affords an optimum cooling, which is better at higher speed than atlow speed.

In total, therefore, the following speed steps are achievable: slipspeed, increased slip speed and direct connection of the drive shaft tothe output shaft 8 with the friction disk clutch 13 engaged.

The embodiment of a drive system 22 according to FIG. 2 differs from theembodiment according to FIG. 1 in that the friction clutch comprisesonly one selectively engageable eddy current clutch 18. A friction diskclutch 13 is provided in just the same way.

This also allows three speeds to be achieved, however. In the case of afirst speed the friction disk clutch 13 and also the eddy current clutch18 are disengaged. However, a speed of the drive shaft 7 is transmittedto the output shaft 8 with a certain, slight slip speed due to thebearing friction, since rotating drive-side parts are supported on theoutput shaft 8 and a catching effect of the output shaft 8 can occur dueto the bearing friction.

A second slip speed is obtained when the selectively engageable eddycurrent clutch 18 is engaged.

The third speed is the direct connection of the drive shaft 7 to theoutput shaft 8 via the engaged friction disk clutch 13.

In a further embodiment of a drive system 23 according to FIG. 3 thedifference compared to the embodiment according to FIG. 1 is that thefriction clutch 5 is two-stage.

As in FIG. 1 it comprises a selectively engageable friction disk clutch13 with corresponding functionality.

When the friction disk clutch 13 is not engaged, an eddy current clutch24 is permanently engaged, the permanent magnet carrier 25 of which isconnected to the rotor 14. In the event of a speed differential betweenthe drive shaft 7 and the output shaft 8 this results on the drive sidein an interaction with the cooling ring 11.

In all three embodiments 1, 22, 23 of a drive system the cooling ring 11is always arranged on the drive side. Furthermore the eddy current zonesare basically formed in this one cooling ring 11.

The design of the embodiment according to FIG. 3 is furthermore suchthat a selectively engageable, second eddy current clutch 18 could beincorporated by building in additional components.

Various clutch modifications can thereby be achieved using largely thesame components, as it were on the modular construction principle.

A further important aspect of the clutches according to FIGS. 1 to 3 isthat the friction clutch 5 is directly connected to the angular gearmechanism 4, the friction clutch 5 on the drive side being attached tothe angular gear mechanism. There is therefore no exposed shaft sectionof the drive shaft 8. The clutch 5 is preferably flanged-mounteddirectly on to the angular gear mechanism 4. This has the advantage of aconstruction that is not only compact but also particularly stable.

The arrangement of the angular gear mechanism 4 and the friction clutch5 is also correspondingly configured in FIG. 4.

This embodiment differs from the embodiment according to FIG. 1 in thatthe friction clutch 5 now only comprises the friction disk clutch 13, sothat a speed of the drive shaft 7 can either be connected to the outputshaft 8 or disconnected. There is therefore only one speed step.

The invention claimed is:
 1. A friction clutch having a drive side, anoutput side for driving a fan impeller, and a selectively engageablefriction disk clutch which in the engaged state connects the output sideto the drive side, a first eddy current clutch for providing a slipspeed on the output side, the first eddy current clutch having an eddycurrent zone formed on a cooling ring, wherein an eddy current zone of asecond eddy current clutch is on the same cooling ring on which the eddycurrent zone for the first eddy current clutch is formed.
 2. The clutchas claimed in claim 1, further comprising the second eddy current clutchwhich can be selectively engaged.
 3. The clutch as claimed in claim 1,wherein the friction disk clutch and/or the second eddy current clutchcan be electromagnetically engaged and disengaged.
 4. The clutchaccording to claim 1, wherein the cooling ring forms the drive side ofthe clutch.
 5. The clutch as claimed in claim 1, wherein a rotor of thefriction clutch interacts with an armature disk and forms the outputside.
 6. The clutch as claimed in claim 1, wherein two separate magneticfield conduction means are provided in the cooling ring.
 7. A drivesystem for cooling an internal combustion engine of a vehicle,comprising a clutch as claimed in claim 1 arranged between a fanimpeller and a drive side of the fan impeller.
 8. A drive system for thecooling of an internal combustion engine of a vehicle, in which anangular gear mechanism and a clutch as claimed in claim 1 are providedbetween a fan impeller and a drive side of the fan impeller, the clutchdirectly abutting the angular gear mechanism on the drive side.
 9. Theclutch as claimed in claim 1, wherein the eddy current zone of the firsteddy current clutch and the eddy current zone of the second eddy currentclutch are spaced radially from each other.